In a wireless communication system, carrier sense is performed as one of technologies for avoiding collision. The carrier sense is processing to confirm that another terminal does not perform transmission in a frequency channel used. A terminal performs wireless transmission when another terminal does not perform transmission, while it suppresses wireless transmission when another terminal performs transmission. The wireless communication system uses the carrier sense to avoid interference due to wireless transmission performed by a plurality of terminals using the same wireless resource (frequency, time).
When the interference occurs, a terminal on the reception side receives desired signals and interference signals at the same time, and a signal-to-noise (SN) ratio is reduced. When the SN ratio is reduced excessively, the reception of desired signals becomes difficult and, consequently, wireless communication becomes difficult. Then, the technology of avoiding interference using carrier sense is developed.
For example, the following Patent Literature 1 discloses a technology in which a base station in a wireless local area network (LAN) controls signal detection thresholds of belonging terminals so that the belonging terminals detect each other to avoid a hidden terminal problem.